Soil and water contamination due to spillage of volatile chemicals has long posed a serious problem in the obtainment of clean drinking and irrigation water. Initial studies in the contaminant removal area were conducted near landfill sites where migration of methane through the soil caused water and soil contamination in adjacent areas. The results of these studies may be found in various trade publications, referenced in my U.S. Pat. No. 4,730,672, issued Mar. 15, 1988.
There are several methods which have previously been used to remove industrial pollutants from contaminated earth strata both above the water table (vadose zone) and below the water table. The most common of these methods is excavation in which all of the contaminated soil is removed and eventually replaced with fresh earth. While excavation is a relatively simple process, it is not practical when large volumes are involved due to prohibitive cost and time factors.
Another method involves a circulation system for leaching contaminants from the vadose layer into the water table where they are recovered by a water removal well and a pump. This process is shown generally in U.S. Pat. No. 4,167,973 as well as other patents. Such processes are not always successful due to low water solubility of most common industrial pollutants, which results in lengthy and often costly recovery.
A third method involves the creation of a vacuum within a withdrawal well in the vadose zone. By injecting air into the soil at points surrounding the withdrawal well, contaminants are urged towards the withdrawal well where they are vaporized and collected by vacuum withdrawal. Such method is described in U.S. Pat. No. 4,183,407 and 4,593,760. These methods are generally effective in contaminant recovery but do not provide for satisfactory disposal of most contaminants.